Oregon Caves weather the passage of time

A broken stalagmite from the Oregon Caves is shedding light on climate change in the Pacific Northwest over the past 13,000 years.

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By Paul Fattig

MailTribune.com

By Paul Fattig

Posted Jan. 13, 2013 at 2:00 AM
Updated Jan 14, 2013 at 3:07 PM

By Paul Fattig

Posted Jan. 13, 2013 at 2:00 AM
Updated Jan 14, 2013 at 3:07 PM

» Social News

A broken stalagmite from the Oregon Caves is shedding light on climate change in the Pacific Northwest over the past 13,000 years.

An analysis of the 50-pound formation by five scientists, studying isotope samples taken from the stalagmite core, indicates that a tiny change in sunlight over time can significantly alter the climate. As a result, resource managers may want to consider the potential for climate change in long-term plans that should be spread out over decades, even centuries, suggests one of the researchers.

The researchers included Oregon State University graduate student Vasile Ersek, now at England's Oxford University, along with Alan Mix and Peter U. Clark, professors in ocean ecology and biogeochemistry at OSU. Other scientists working on the project were Hai Cheng and Lawrence Edwards from the University of Minnesota.

A $650,000 National Science Foundation grant funded the study. An article on the study co-written by the five scientists was published Nov. 27 in the science journal Nature Communications.

"What the work shows is that winter rain/snow sources in Southern Oregon are very sensitive to change and are quite variable," Mix wrote in an email to the Mail Tribune.

In the prehistoric record written in stone at the Oregon Caves, warmth is generally associated with dry conditions, he noted.

"This is likely linked into some relatively large-scale circulation patterns," he wrote. "High sensitivity to change implies the potential for future changes, whether that is a response to human-caused climate change, or natural climate variability, both of which are phenomena widely accepted by the scientific community."

Although stressing he would be very cautious about making climate predictions based on their research, he indicated the data will help test models to simulate longterm climate variability.

"So taking all of this to the management perspective that people care about, it would be wise to build uncertainty and the potential for variability into longterm resource allocation plans," he concluded, noting those plans should be on the scale of many decades to many centuries or longer.

Stalagmites, which rise from the floor of a cave, grow as the result of minerals in the water dripping down from above, explained geologist John Roth, a natural resources specialist at Oregon Caves National Monument. He and other monument staff members provided logistical support and took samples during the research.

In the Oregon Caves, a stalagmite's growth occurs largely between November and June when storms drop rain or snow, soaking the ground and creating drip water in the caves, he said.

As a result of that extremely slow annual growth, scientists are able to study the ratios of different isotopes of carbon and oxygen trapped in the limestone, he added.

"Such changes over time in these rock mounds help climatologists figure out how hot it was and how much rain fell," he said.

Like ice core samples taken from glaciers in Greenland or Antarctica, the stalagmite reflects climate change over the eons, Roth said.

"This treasure trove of sharply imaged data will yield new ways to understand climate for many years to come," he said of the research.

"This study better refines what the natural cycles are," he said. "It appears pretty convincing based on this evidence that solar-cycle increase does affect the weather."

Two earlier climate studies in the caves looked at rock formations but were not as extensive, he said, noting this studied both precipitation and temperature changes over a long period.

"This is brand new stuff," Roth said. "It is the only one with this amount of detail on the West Coast. This puts us on the map when it comes to science."

The stalagmite used in the research was likely broken off during the initial trail construction in the caves during the 1930s, he said.

"We wanted to use something that had already been broken," he noted.

The study doesn't address whether the rise in greenhouse gases has affected the cycle in the last century, Roth said.

"Unfortunately, the Oregon stalagmites' calcite stopped growing during this time interval," he said of the past 100 years. "Nevertheless, the earlier cycles suggest that the solar cycle change of just a few tenths of one percent of sunlight energy reaching Earth may be amplified into much greater climate and ocean changes.

"The human-caused greenhouse effect likely has already added at least that amount of energy, suggesting that further changes in Oregon's climate are likely," he added.

There is no doubt the climate is changing, he said.

"You go back to the 1930s, and they were shoveling snow off the chateau roof because they were afraid it would collapse under the snow," Roth said. "We don't have that concern now."